How can i animate multiple objects to give an explosion effect?
For a 'dumb' explosion effect, you could try keyframing the objects, then scale their centers, so they all move away from the center. This would give some control over the speed of the 'explosion'. But, this technique has no dynamics. So, the shrapnel would not react to other objects. but it might work well for mechanical drawings.

make sure the 'Manipulate Cneter Points' button is checked.



select all the objects. (I used Cube, applied 3 array modifiers, and separated loose parts.)



Add a keyframe with I-Key. select location.



Move to a later point in the timeline and Scale larger.



Add another keyframe.

The objects are 'exploded'.

If you have an object on center (0,0,0), it will not move. You can change this by scaling from the 3d cursor.